Railway car



'7 Sheets-Sheet l INVENTOR HAI-CHAN@ BENJAMIN Koo Bylu m ATTORNEY HAI-CHANGE BENJAMIN KOO RAILWAY CAR \I II I IIIILTIILIIISIMT HMIIIIHIIMIIIIIMHHHHI pri N, 1967 Filed Mays, 1955 April u, 1967 HAl-cHANG BENJAMIN Koo 3,333,246

RAILWAY CAR '7 Sheets-Sheet 2 Filed May I5, 1955 Apr M, m6? HAI-CHAN@ BENJAMAN Kao 3,3%355 RAILWAY CAR 7 Sheets-Sheet 5 Filed May I5, 1965 pri u, w67

HAI-CHANCE BENJAMlN KOO RAILWAY CAR '7 Sheets-Sheet 4 Filed May 5, 1965 8k Q QN HAI-CHANCE BENJAMIN KOO RAILWAY GAR Filed May .'5, 1965 7 Sheets-Sheet ...IMWWWWWMWH pil H, 1967 HAi-CHANG BENJAMIN Koo 3,313,246

RAILWAY CAR Filed May 3, 1965 ',7 Sheets-Sheet 6 FIG. 9.

Amig M 1967 HAi-CHANG BENJAMIN Koo 33H24@ RAILWAY CAR v Filed May s, 1965 7 sheets-sheet 7 United States Patent O 3,313,246 RAILWAY CAR Hai-Chang Benjamin Koo, Toledo, Ohio, assignor to ACF Industries, Incorporated, New York, NX., a corporation of New Jersey Filed May 3, 1965, Ser. No. 452,439 4 Claims. (Cl. 10S-454) T'nis invention relates to a railway car and more particularly to a railway car employing a cushioned underfrarne having a sliding center sill arrangement.

Heretotore, in a cushioned underfrarne railway car having a sliding sill arrangement, the sliding sill has been of a generally rigid uniform cross section extending along the longitudinal centerline of the car for the length thereof and positioned closely adjacent a iixed center sill. When impact forces were exerted against such a railway car from its couplers, the forces were transmitted from the sliding sill and cushioning unit to the xed sill and underrame. As the sliding sill has been generally rigid heretofore, only a minimum amount of the force has been dissipated by iiexure of the sliding sill. Further, sills in cushioned undertrame cars heretofore have been of a substantial vertical dimension and have extended through the center ot the bolsters. This has necessitated the bolsters being of a certain minimum height to receive the sliding sill.

rI`he present construction is particularly adaptable for utilization in the forming of relatively long length cars such as eighty-tive (85) feet or over in overall length. The construction is also particularly adapted for use in railway cars having a low center of gravity and especially where the car couplers are mounted within housings that project above the deck or door or the car. The height ot the car couplers at the present time is iixed by existing standards at two feet, ten and one halt inches (2', lOl/2") above the rails and the center of gravity of the underframe is along a neutral axis below the height at which impact forces are exerted through the car couplers. Such a design produces an eccentricity exerted about the couplers which must be dissipated into the car undertrarne. The longitudinal or axial forces exerted by the couplers are transmitted to the sliding sill arrangement and has a neutral axis only slightly below the centerline of the couplers.

`It is an object of the present invention to provide a cushioned underframe railway car having a sliding sill arrangement for a relatively long length railway car with a relatively low center of gravity.

A further object of this invention is the provision of such a cushioned underframe car in which the sliding sill arrangement is of a minimum vertical dimension thereby to malte it particularly adaptable for use in a railway car having a relatively low center of gravity.

An additional object of this invention is the provision of a long length iiat car having a sliding sill arrangement in which the sliding sill is permitted to iiex for dissipating a portion of the draft and but forces independently of the underframe, and then to ex with the underframe to dissipate the remaining portion of the forces transmitted from the car couplers.

A further object is the provision of an underframe having a sliding sill arrangement in which the sliding sill is designed especially to avoid passing through the center of the bolsters while permitting the utilization of -a at car having a relatively low deck height.

Briefly, the invention comprises a cushioned underframe car having a sliding sill arrangement mounted relative to the underframe so that the sliding sill may ex relative to the underirame at a position intermediate the bolsters for a predetermined distance to dissipate at least a portion of the forces transmitted to the sliding sill from the car couplers. Then, the sliding sill flexes with the ICC underframe after the exure of said predetermined amount to dissipate the remainder of the forces transmitted to the sliding sill. The sliding sill arrangement comprises a pair of spaced parallel tubular portions extending between the holsters and connected to 'a yoke outboard of each bolster thereby to pass through the holsters at a position remote from the centerline thereof.

The provision of a resilient sliding sill which is permitted to ex a predetermined amount relative to the underframe minimizes binding between the sliding sill structure and the xed underframe when impact forces are dissipated. Even if binding does occur between the sliding sill structure and the fixed underframe upon the exertion of a relatively high impact force, the resilient sliding sill structure quickly returns t0 its original position upon the dissipation of the impact force.

The invention accordingly comprises the elements and combination of elements, features of construction, and arrangement of parts which will be exemplied in the structures hereinafter described, and the scope of which will be indicated in the following claims.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

FIGURES 1 and 1A are top plans of a railway flat car comprising the present invention and cooperatively showing the entire length of the flat car;

FIGURES 2 and 2A are side elevations cooperatively showing the railway at car of FIGURES l and 1A;

FIGURE 3 is a section taken generally along line 3-3 of FIGURE l;

FIGURE 4 is a section taken generally along line 4-4 of FIGURE 1;

FIGURE 5 is a section taken generally along line 5-5 of FIGURE l;

FIGURE 6 is an enlarged plan View with certain parts broken way and showing the center of car cushioning;

FIGURE 7 is an enlarged side elevation of the center of car cushioning shown in FIGURE 6;

FIGURE 8 is a section taken generally along line 8 8 of 'FIGURE 6;

FIGURE 9 is a section taken generally along line 9 9 of FIGURE 6 and showing the connection of the tubular sliding sill members to the abutment member for the cushioning unit;

FIGURE l0 is a section taken generally along the line lil- I0 of FIGURE 6 and showing the support for the center of car cushioning unit;

FIGURE ll isV a top plan of the end portion of the sliding center sill structure shown removed from the underframe;

FIGURE l2 is a side elevation of the sliding center sill structure shown in FIGURE ll;

FIGURE 13 is a section taken 13-I3 of FIGURE 11;

FIGURE 14 is a section taken 14-I4 of FIGURE l1;

FIGURE l5 is a schematic of the sliding sill and cushioning unit with the sliding sill shown in a neutral position; and

FIGURE 16 is a schematic similar to FIGURE l5 but showing the sliding sill and cushioning unit after the sliding sill has been subjected to impact forces.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now to the drawings for better understanding of my invention, and more particularly to FIGURES 1-5, a railway ilat car of the so-called low level type is indicated at I0 and has a truck I2 adjacent each end thereof. An underframe indicated generally at 14 is mounted on trucks I2 and comprises a xed center sill structure which includes an end section at each end generally along line generally along line thereof generally designated 16 and an intermediate section generally designated 18. A oor or deck 20 extends the length of underframe 14 and a draft gear housing 22 projects above the deck as shown in FIGURES 1 and 1A. A channel-shaped side sill member 24 extends along each side of underframe 14 and forms a box-shaped structure with deck 20. A side guide rail 25 extends along each side of the underframe upwardly from the upper surface of deck 20. The inner end of draft gear housing 22 is tapered as indicated in FIGURE 2A and a suitable riser board (not shown) may be positioned on deck 20 adjacent each side of housing 22 to provide adequate clearance for a tractor or the like passing over housing 22.

As shown in FIGURE 5, end section 16 of the xed center sill structure includes spaced lower plates 26 and vertical webs 28 extending between deck 26 and plates 26. Cross members 30 extends between outer webs 23 and side sills 24.

Referring to FIGURE 3, a bolster center plate 32 is secured to a bottom cover plate 34 of the xed sill structure which forms a continuation of plates 26 and has an opening 36 for receiving the kingpin of truck 12. Transversely extending vertical webs 38 have openings 40 therein and an upper cover plate 42 extends over webs 33. The fixed center sill structure is bifurcated inwardly of the bolster structure to form intermediate section 18 of a pair of spaced intermediate fixed sills 43. As shown in FIGURES 4 and 8, each sill 43 comprises a vertical web 44 and a lower plate 46. Extending between and outwardly of sills 43 are crossbearers 47. Stringers 4S may, if desired, be provided as stitfeners to extend longitudinally of underframe 14.

Forming an important feature of this invention, a sliding sill structure is indicated generally at Si) and comprises an end section 52, a transition section 54, and an intermediate section 56 as shown particularly in FIG- URES 11 and 12. End section 52 is box-shaped to receive a coupler and draft gear structure 57 and tapers from a full cross section as shown in FIGURE 5 to an intermediate cross section as shown in FIGURE 14. A small diameter cross section is shown in FIGURE 13. Extending frorn each side 58 of end section 52 is an upper lip 60 and a lower lip 62 reinforced by connecting ribs 64. Lower lips 62 rest on lower plates 26 to support the sliding sill structure 50 for sliding movement relative to underframe 14. Upper lips 60 are spaced from the lower adjacent surface of oor 20 a predetermined distance and are adapted to contact floor 20 upon flexure of sliding sill structure 59 as will be explained fully below.

Transition section 54 is a cast yoke forming bifurcated legs 66. Each leg 66 has a reduced diameter end 63. Fitting around each end 68 is a tubular intermediate sliding sill 70 of a circular cross section forming intermediate section 56. Suitable bolt and nut combinations 72 secure each sill 70 to transition section 54. As shown in FIG- URES 1 and 3, transition section 54 is positioned outboard of the adjacent bolster structure and tubular sliding sills 70 extend through openings 40 in webs 38. As sills 70 are of a relatively small vertical dimension the bolster structures need be only a relatively small depth.

As shown in FIGURE 4, tubular sills 70 pass through openings 74 in cross member 47. To determine accurately the diameter of each opening 74 an apertured bearing plate or sleeve 76 is secured, such as by welding, to the face of cross member 47 and forms opening 74. To reinforce each sleeve 76, ribs 7S are provided. Sleeves 76 are positioned on cross members 47 so that a line contact is provided between tubular sliding sills 70 and sleeves 76 thereby to have a minimum amount of frictional contact upon relative movementof sliding sill structure Sil.

Referring to FIGURES 6, 7, 9 and 10, a center of car cushioning unit is indicated generally at 80 and comprises an outer cylinder S2 receiving an inner cylinder S4. Cushioning unit 80 may be of the oleopneumatic type in which cylinder S4 may contain a relatively compressible fluid, such as air or dry nitrogen gas, and cylinder 82 may contain a relatively incompressible liquid, such as hydraulic iiuid, with a movable oating piston separating the fluids. For further details of the cushioning unit, reference is made to Patent No. 2,994,442 issued Aug. 1, 1961 and entitled, Kinetic Energy Absorbing Device, the entire disclosure of which is incorporated by this reference.

Outer cylinder 82 has an end cap S3 and inner cylinder 84 has an end cap 90. Fixed abutments 92 and 94 adjacent respective end caps 88, have respective reinforcing webs 6 and 9S secured to plate 99 on the undersurface of floor 2@ and to the adjacent cross members 47.

Contacting cylinders 82 and 34 are respective movable abutments 11b!) and 192 which abut respective end caps 83 and Si). Abutments 169 and 192 each comprises a casting having a bore 194 in which the ends of tubular sills 70 are secured by a suitable nut and bolt combination 166 as shown in FIGURE 9. Connecting tubular sills 70A extend between castings 10i), 1512 and are likewise secured by suitable nut and bolt combinations. As shown in FIGURES 6 and 10, partial cross members 47A have sleeves 76A receiving tubular sliding sills 70A for sliding movement. To support cushioning unit 80, a bottom plate 193 beneath unit 30 is supported by an I-beam 110. Carrying plate 103 are side channels 112 each having its lower iiange cutaway at the end corners of the channel. A clip plate 114 is welded to the outer face of each channel 112 in the area defined by the cutaway lower flange and to the outer face of the adjacent casting or 102. Thus, side channels 112, I-beam 110, and support plate 108 move with sliding sl structure 50 relative to underframe 14.

Referring to FIGURES 15 and 16, the movement of sliding sill structure 5t) is shown schematically. FI-Gf URE 15 shows sliding sill structure Si) in a neutral or rest position with movable abutments and fixed abutment 92 in contact with end cap S8 of cylinder S2. Movable abutments 162 and fixed abutment $4 are in contact with end cap 911 of inner cylinder 84.

FIGURE 16 shows the position of sliding sill structure' 50 and cushioning unit Si) after an impact from the left; viewing FIGURE 15. Fixed abutment 94 restrains the movement of inner cylinder 84 and movable abutments 100 move outer cylinder 82 to the right viewing FIGURE 16. Similarly, upon an impact from the right viewing FIGURE 15, xed abutment 92 restrains the movement of outer cylinder 82 and inner cylinder 84 moves with the movable abutments 102.

Sliding center sill structure 50 is resilient and formed preferably of a high strength low alloy steel. Thus, upon impact forces exerted against sliding sill structure, a bending or flexing occurs. It is desirable to have a predetermined limited amount of exure relative to underframe 14 and for that purpose openings 40 in bolster webs 38 and openings 74 in sleeves 76 are of a diameter slightly greater than the outside diameter of tubular sills 70, 70A. For example, tubular sills 70, 70A may be of an outside diameter of tive and one-half (5l/z) inches with openings 38, 74 of an inside diameter of around six (6) inches. Upon impact forces exerted against the sliding sill structure 50, tubular sills 70, 70A tend to bend in a sinuous or wave pattern with sills 70, 70A contacting the upper portions of some sleeves 76 and the lower portions of other sleeves 76. Since tubular sills 70, '70A are of a circular cross section, texure may occur in any direction and sometimes the lateral portions of sleeves 76 are contacted by sills 70, 70A upon flexure. After tubular sills 70, 70A fiex a predetermined amount and are in rm Contact with sleeve 76, the underframe 14 bends with sliding sill structure 50 until the remainder of the forces is dissipated. Underframe 14 may flex for two or three inches.

Referring to FIGURES 5, 11 and 12, lower lip 62 is shown resting on lower plates 2S of the fixed underframe 14. The centerline of coupler structure 57 is around two and one-half (2l/2) inches above the longitudinal axis of tubular intermediate sills 56 and thus, an eccentricity is exerted upon sliding sill structure Sil to provide a bending action. To aid in dissipating a portion of the forces resulting from the eccentricity, upper lips 60 contact the upper lower surface of plate or floor 20 upon the bending of center sill structure S0 to restrain the bending of end section 52 of the sliding center sill structure 50.

The sliding sill structure 50 has portions connected by nut and bolt combinations 72 and 10e and may be inserted in position after the construction of underframe 14. Also, if desired, the sliding sill structure 50 may be removed from underframe 14 upon removal of nut and bolt combinations 72, 166 and the removal of clip plates 114 from adjacent castings 102.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A low level railway flat car comprising, an underframe, a generally liat deck over the undertrame, a coupler at each end of the car, a draft gear housing projecting above the upper surface of the deck, a xed center sill structure extending the length of the underframe, a bolster structure adjacent each end of the underframe, a sliding center sill structure extending the length of the underframe generally in alignment with the longitudinal centerline of the couplers and adapted to move relatively to the iixed sill structure and underframe upon impact forces being exerted against the railway car, and cushioning means between the sliding sill structure and the underframe to provide cushioned movement of the sliding sill structure, said sliding center sill structure comprising an end section adjacent each end of the underframe positioned centrally of the width of the car outboard of the adjacent bolster structure, and a pair of horizontally spaced intermediate sliding sill members extending between the end sections and passing through the bolster structures, said cushioning means -being positioned between the spaced intermediate sliding sill members generally centrally of the length ofthe underfrarne to cushion the movement of the sliding sill structure, said sliding center sill structure iitting within said draft gear housing and having an upper and lower lip projecting from each side thereof, the lower lips being supported on said underframe and mounting the sliding center sill structure for sliding movement, the upper lips being closely spaced from the superjacent flat deck whereby upon the exertion of impact forces and iiexure of the sliding sill structure the upper lips engage the superjacent deck to restrain the liexure of said center sill structure.

2. A railway liat car comprising, a cushioned underframe, a generally liat deck over the underframe, a draft gear housing projecting above the upper surface of the deck, a iixed center sill structure extending the length of the underframe, a bolster structure adjacent each end of the underfranie, a sliding center sill structure extending the length of the underframe and adapted to move relatively to the xed sill structure and underframe upon the exertion of impact forces against the railway car, a cushioning unit between the sliding sill structure and the underframe to provide cushioned movement of the sliding sill structure, said sliding center sill structure comprising an end section adjacent each end of the undertrame positioned centrally of the width of the car outboard of the adjacent bolster structure and a resilient intermediate section extending between the end sections passing through the bolster structures, and means on the underframe providing a clearance between at least a major portion of the length of said intermediate section and the underframe to permit a tlexure of the intermediate section relative to the underframe upon the exertion of impact forces against the railway car, said sliding center sill structure iitting within the draft gear housing and having a lip projecting from each side thereof closely spaced from the superjacent undersurface of the deck whereby upon the iiexure of the sliding center sill structure the lips engage the deck to restrain the ilexure of said sliding center sill structure relative to the underframe.

3. In a cushioned -underframe for a railway car, a lixed center sill structure extending the length of the underframe, a bolster structure adjacent each end of the underframe, a sliding center sill structure extending the length of the underframe and adapted to move relatively to the fixed sill structure and underframe upon the exertion of impact forces against the railway car, said sliding center sill structure comprising a pair of end sections, a pair of adjacent connecting transition sections, and an intermediate section, said end sections being positioned adjacent the ends of the underframe centrally of tbe width of the car outboard of the adjacent bolster structure and being tubular in cross section at least adjacent the inner ends thereof, said intermediate sliding sill section having a pair of horizontally spaced, resilient intermediate sliding sill members of a tubular cross section passing through the bolster structures, said transition sections being of a tubular cross section and positioned between the inner ends of the end sections and the intermediate sliding sill section, each transition section having a pair of bifurcated tubular legs, means to secure the intermediate tubular sill members to the tubular bifurcated legs in a telescoped position, cushioning means positioned between the spaced intermediate sliding sill members intermediate the length of the underframe to cushion the movement of the sliding sill structure, a plurality of cross-bearers spaced along the length of the underframe between the bolster structures each having a generally vertical web, said vertical webs having openings therein to receive the intermediate tubular sliding sill members, and separate bearing members for said intermediate sliding sill members secured to said vertical webs and aligned with the adjacent vertical web openings for guiding and accurately positioning the intermediate sliding sill members, said tubular intermediate sill members being of a cross-sectional area substantially less than the area of the openings in the bearings and vertical webs for providing clearance to permit a limited predetermined tlexure of said sliding sill structure relative to and independent of the underframe thereby to absorb at least a portion of the impact forces, an additional iiexure of said sliding sill structure after said predetermined flexure eiiecting contact of the sliding sill structure with said bearings at said vertical web openings thereby to provide iiexure of said sliding sill structure with the underframe.

4. In a cushioned underframe for a railway car as set forth in claim 3, said intermediate tubular sill members being circular in cross section and said bearings comprising sleeves receiving the intermediate tubular sill members and axially aligned with the vertical web openings.

References Cited by the Examiner UNlTED STATES PATENTS 1,027,323 5/1912 Dambino 213-8 1,233,999 7/1917 Ferguson 213-8 2,132,232 10/1938 Duryea 213-8 3,166,200 1/1965 Danielson 213-8 3,207,086 9/ 1965 MoWatt-Larssen et al. 10S-368 3,209,708 10/ 1965 Spence 10S-454 3,221,898 12/1965 Pellnitz 213-88 3,223,052 12/ 1965 Gutridge et al. 10S-454 EUGENE G. BOTZ, Primary Examiner.

DRAYTON E. HOFFMAN, Examiner. 

1. A LOW LEVEL RAILWAY FLAT CAR COMPRISING, AN UNDERFRAME, A GENERALLY FLAT DECK OVER THE UNDERFRAME, A COUPLER AT EACH END OF THE CAR, A DRAFT GEAR HOUSING PROJECTING ABOVE THE UPPER SURFACE OF THE DECK, A FIXED CENTER SILL STRUCTURE EXTENDING THE LENGTH OF THE UNDERFRAME, A BOLSTER STRUCTURE ADJACENT EACH END OF THE UNDERFRAME, A SLIDING CENTER SILL STRUCTURE EXTENDING THE LENGTH OF THE UNDERFRAME GENERALLY IN ALIGNMENT WITH THE LONGITUDINAL CENTERLINE OF THE COUPLERS AND ADAPTED TO MOVE RELATIVELY TO THE FIXED SILL STRUCTURE AND UNDERFRAME UPON IMPACT FORCES BEING EXERTED AGAINST THE RAILWAY CAR, AND CUSHIONING MEANS BETWEEN THE SLIDING SILL STRUCTURE AND THE UNDERFRAME TO PROVIDE CUSHIONED MOVEMENT OF THE SLIDING SILL STRUCTURE, SAID SLIDING CENTER SILL STRUCTURE COMPRISING AN END SECTION ADJACENT EACH END OF THE UNDERFRAME POSITIONED CENTRALLY OF THE WIDTH OF THE CAR OUTBOARD OF THE ADJACENT BOLSTER STRUCTURE, AND A PAIR OF HORIZONTALLY SPACED INTERMEDIATE SLIDING SILL MEMBERS EXTENDING BETWEEN THE END SECTIONS AND PASSING THROUGH THE BOLSTER STRUCTURES, SAID CUSHIONING MEANS BEING POSITIONED BETWEEN THE SPACED INTERMEDIATE SLIDING SILL MEMBERS GENERALLY CENTRALLY OF THE LENGTH OF THE UNDERFRAME TO CUSHION THE MOVEMENT OF THE SLIDING SILL STRUCTURE, SAID SLIDING CENTER SILL STRUCTURE FITTING WITHIN SAID DRAFT GEAR HOUSING AND HAVING AN UPPER AND LOWER LIP PROJECTING FROM EACH SIDE THEREOF, THE LOWER LIPS BEING SUPPORTED ON SAID UNDERFRAME AND MOUNTING THE SLIDING CENTER SILL STRUCTURE FOR SLIDING MOVEMENT, THE UPPER LIPS BEING CLOSELY SPACED FROM THE SUPERJACENT FLAT DECK WHEREBY UPON THE EXERTION OF IMPACT FORCES AND FLEXURE OF THE SLIDING SILL STRUCTURE THE UPPER LIPS ENGAGE THE SUPERJACENT DECK TO RESTRAIN THE FLEXURE OF SAID CENTER SILL STRUCTURE.
 3. IN A CUSHIONED UNDERFRAME FOR A RAILWAY CAR, A FIXED CENTER SILL STRUCTURE EXTENDING THE LENGTH OF THE UNDERFRAME, A BOLSTER STRUCTURE ADJACENT EACH END OF THE UNDERFRAME, A SLIDING CENTER SILL STRUCTURE EXTENDING THE LENGTH OF THE UNDERFRAME AND ADAPTED TO MOVE RELATIVELY TO THE FIXED SILL STRUCTURE AND UNDERFRAME UPON THE EXTERTION OF IMPACT FORCES AGAINST THE RAILWAY CAR, SAID SLIDING CENTER SILL STRUCTURE COMPRISING A PAIR OF END SECTIONS, A PAIR OF ADJACENT CONNECTING TRANSITION SECTIONS, AND AN INTERMEDIATE SECTION, SAID END SECTIONS BEING POSITIONED ADJACENT THE ENDS OF THE UNDERFRAME CENTRALLY OF THE WIDTH OF THE CAR OUTBOARD OF THE ADJACENT BOLSTER STRUCTURE AND BEING TUBULAR IN CROSS SECTION AT LEAST ADJACENT THE INNER ENDS THEREOF, SAID INTERMEDIATE SLIDING SILL SECTION HAVING A PAIR OF HORIZONTALLY SPACED, RESILIENT INTERMEDIATE SLIDING SILL MEMBERS OF A TUBULAR CROSS SECTION PASSING THROUGH THE BOLSTER STRUCTURES, SAID TRANSITION SECTIONS BEING OF A TUBULAR CROSS SECTION AND POSITIONED BETWEEN THE INNER ENDS OF THE END SECTIONS AND THE INTERMEDIATE SLIDING SILL SECTION, EACH TRANSITION SECTION HAVING A PAIR OF BIFURCATED TUBULAR LEGS, MEANS TO SECURE THE INTERMEDIATE TUBULAR SILL MEMBERS TO THE TUBULAR BIFURCATED LEGS IN A TELESCOPED POSITION, CUSHIONING MEANS POSITIONED BETWEEN THE SPACED INTERMEDIATE SLIDING SILL MEMBERS INTERMEDIATE THE LENGTH OF THE UNDERFRAME TO CUSHION THE MOVEMENT OF THE SLIDING SILL STRUCTURE, A PLURALITY OF CROSSBEARERS SPACED ALONG THE LENGTH OF THE UNDERFRAME BETWEEN THE BOLSTER STRUCTURES EACH HAVING A GENERALLY VERTICAL WEB, SAID VERTICAL WEBS HAVING OPENINGS THEREIN TO RECEIVE THE INTERMEDIATE TUBULAR SLIDING SILL MEMBERS, AND SEPARATE BEARING MEMBERS FOR SAID INTERMEDIATE SLIDING SILL MEMBERS SECURED TO SAID VERTICAL WEBS AND ALIGNED WITH THE ADJACENT VERTICAL WEB OPENINGS FOR GUIDING AND ACCURATELY POSITIONING THE INTERMEDIATE SLIDING SILL MEMBERS, SAID TUBULAR INTERMEDIATE SILL MEMBERS BEING OF A CROSS-SECTIONAL AREA SUBSTANTIALLY LESS THAN THE AREA OF THE OPENINGS IN THE BEARINGS AND VERTICAL WEBS FOR PROVIDING CLEARANCE TO PERMIT A LIMITED PREDETERMINED FLEXURE OF SAID SLIDING SILL STRUCTURE RELATIVE TO AND INDEPENDENT OF THE UNDERFRAME THEREBY TO ABSORB AT LEAST A PORTION OF THE IMPACT FORCES, AN ADDITIONAL FLEXURE OF SAID SLIDING SILL STRUCTURE AFTER SAID PREDETERMINED FLEXURE EFFECTING CONTACT OF THE SLIDING SILL STRUCTURE WITH SAID BEARINGS AT SAID VERTICAL WEB OPENINGS THEREBY TO PROVIDE FLEXURE OF SAID SLIDING SILL STRUCTURE WITH THE UNDERFRAME. 